Officials inspect an All Nippon Airways Boeing 787 which made an emergency landing at Takamatsu airport in Takamatsu, western Japan, earlier this month. / AP

by Bart Jansen, USA TODAY

by Bart Jansen, USA TODAY

Boeing announced record revenues for 2012 on Wednesday, but said it isn't sure yet what caused the problem that grounded its 787 Dreamliners or when it will be fixed.

But, the company said, problems with the lithium-ion batteries on the plane haven't changed their plans to step up production of the sophisticated jetliner.

CEO Jim McNerney said the company is working with investigators at the National Transportation Safety Board, their Japanese counterparts and the Federal Aviation Administration to find the problem that caused battery fires on two planes earlier this month. McNerney said Boeing experts and investigators are working around the clock.

"We will get to the bottom of this and in so doing, we will restore confidence in the 787 and Boeing," McNerny said during a conference call.

In 2012, production of the Dreamliner increased rate from two to five per month. Despite a halt in delivering the plane, production is on track to reach seven per month in mid-2013 and 10 by end of the year, officials said.

McNerney declined to answer a question about what a six-month delay in finding the problem would mean for the company. He also declined to speculate on the chances that the problem would require a relatively modest software change or a more complicated replacement of the battery or electrical system.

But the company hasn't lost faith in lithium-ion batteries, which are flammable but provide power for the innovative plane that is 20% more fuel-efficient than similar planes.

"Nothing we've learned has told us yet that we have made the wrong choice on the battery technology," McNerney said. "We feel good about the battery technology and its fit for the airplane."

The earnings call coincided with Japan's All Nippon Airways (ANA) announcing that it had replaced lithium-ion batteries on its 787 Dreamliners 10 times because of a low charge before the jets were grounded worldwide on Jan. 16 due to battery problems, the New York Times reported Wednesday.

ANA spokeswoman Megumi Tezuka said Wednesday the airline was not required to report the battery swapping cases to Japan's Transport Ministry because they did not raise safety concerns and did not interfere with flights.

She said the batteries were replaced because they failed to charge properly or showed other problems.

McNerney couldn't say how many Dreamliner batteries have been replaced, but that it is routine for maintenance.

"There has been no incident that we are aware of where our battery has been replaced due to any kind of safety concerns," said McNerney, who calls the rate of Dreamliner replacements "slightly higher" than expected.

A spokeswoman, Kate Bergman, said Boeing replaces about 2,000 batteries a year in its planes.

Kelly Nantel, a spokeswoman for the NTSB, says investigators only recently heard there had been "numerous issues with the use of these batteries," but "that will absolutely be part of the investigation."

All 50 Dreamliners worldwide were grounded after an ANA flight on Jan. 16 made an emergency landing in Japan when its main battery overheated. Earlier, on Jan. 7, a battery in a Japan Airlines 787 caught fire while parked at Boston's Logan International Airport.

In Boeing's fourth quarter earnings report, the company said it earned $1.28 per share vs. Wall Street estimates of $1.19 a share on revenues of $22.4 billion. Excluding pension-related costs, Boeing's profits were up 9% in the fourth quarter vs. the same period a year ago. Revenues hit a record $81.7 billion for the year.

The company delivered more than 600 commercial airliners last year, including the first three Dreamliners built in Charleston. The company expects to deliver 60 per year once the safety investigation is completed.

Shares of Chicago-based Boeing Co. rose 88 cents to $74.53 in morning trading. They've dropped about 4 percent since the battery fire on the plane in Boston.